- Add -h help and usage screen

Doc Notes
---------

- Note that symlinks are not expanded but that targets
  accessed via symlinks are stored to canonical path.

- Test mode has no effect on -d which always works

- If -d is effective immediately upon reading command line so
  you can clean multiple graveyards with:

   /trm.sh -g ./foo -d -g ./baz -d

- Note difference between -vd and -dv

- Note differences between how serial numbers are appended
  on directories vs. files.  Use of find to overcome this.